AJAX autocomplete based on other field value

Question

I'm trying to implement an auto complete form with a little twist. I want its auto complete options to be limited by another field (text field to be more specific).

I understand how AJAX API works and should able to create an auto complete filter for a field based on it's own values but I have no idea how to create a an a auto complete filter based on another field in the form.

From what I have found only this question is similar to my problem, it is unfortunately unanswered. I don't want the code, just hint where to look would be useful.

BTW: I have came up with a solution but it's unbelievably dirty hack that requires going into database twice. I could implement AJAX callback for the field I want the filter to be based on, store the value of the field in the callback to custom database table and then in the callback of the field I want to filter get the value and make it work.

BTW2: The field I want to base the filter on will be text field, the other one custom entityreference.

BTW3: I'm almost sure it is possible somehow since the entityreference option limit module does something like that. (It does it with a help of one other field which I don't want (And I didn't understand it at all even though I tried anyway :) ))

Answer 1

Great job on the research ... here's a solution I came up with. The Drupal Form API and Ajax API should be able to do this but I stopped after I got abit confused too some time ago -- I wrote a fallback using jQuery (which comes bundled with Drupal).

In a custom module .info file I add my javascript:

scripts[] = eap_student_feedback2_ajax.js

You could add this via a form_alter() call instead and using #attached FAPI key.

Then in my javascript file I have dependant dropdowns. You have to select a Country before you select a Program available in that country. When you select a Country, those countries Program list is fetched via Ajax and inserted into that HTML select list -- the widget is then made available. The jQuery code is as follows:

jQuery(function($) {

  $('#edit-field-survey-program-und option:gt(0)').remove();
  $('#edit-field-survey-program-und').attr('disabled', 'disabled');

  $("#edit-field-survey-country-und").click(function() {
    var selected_country = $("#edit-field-survey-country-und").val();
    if (selected_country != '_none') {
      $.ajax({
        type:'GET',
        url: '/eap-ajax/eap-country-programs/' + selected_country,
        data: '',
          success:function(data){
          //console.log("got: ");
          //console.log(data);
          // Do actual work.
          $('#edit-field-survey-program-und option:gt(0)').remove();
          $.each(data, function(key, value) {
            $('#edit-field-survey-program-und').append(
              '<option value="' + key + '">' + value + '</option>'
            );
          });
          $('#edit-field-survey-program-und').removeAttr('disabled');
        }
      }); 
    }
  });
});

In my module file I implement hook_menu to supply the ajax endpoint:

// Make a frigging ajax callback.
function eap_student_feedback2_menu() {
  $items['eap-ajax/eap-country-programs/%'] = array(
    'page callback' => '_eap_student_feedback2_programs_json_endpoint',
    'page arguments' => array(2),
    'type' => MENU_CALLBACK,
    'access callback' => TRUE,
  );
  return $items;
}

And also implement the logic to return some JSON for jQuery:

function _eap_student_feedback2_programs_json_endpoint($country_term_id) {
  $matches = array();
  $result = db_query('
      SELECT tth.tid, ttd.name AS term_name
      FROM taxonomy_term_hierarchy tth
      LEFT JOIN taxonomy_term_data ttd ON tth.tid = ttd.tid
      WHERE tth.parent = :tid
      ORDER BY 2 ASC
  ', array(':tid' => $country_term_id));
  // add matches to $matches
  foreach ($result as $row) {
    $matches[$row->tid] = check_plain($row->term_name);
  }
  // return for JS
  return drupal_json_output($matches);
}

Answer 2

I know it's a bit amateur but the question has already been answered I just didn't find it.

It's here:

form auto complete how to restrict results by previous drop down

and here:

Using ajax to filter drupal autocomplete form

BTW: I would delete the question but since I didn't find the answered questions myself I thought that this one might be more discoverable.

//I can't accept my own answer now, sory for that.